LED UV moisture curing adhesive and preparation method thereof
By introducing a photo-induced latent moisture curing catalyst and a stepwise asymmetric end-capping process, an active linkage mechanism between photocuring and moisture curing was constructed, which solved the problems of slow curing in the shaded area and storage stability, and achieved rapid deep curing and efficient storage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGGUAN GAOTU NEW MATERIAL CO LTD
- Filing Date
- 2026-03-06
- Publication Date
- 2026-05-05
AI Technical Summary
In existing LED UV moisture dual curing systems, the curing reaction in the shaded area is passive and slow, heavily dependent on ambient humidity, and it is difficult to achieve deep and rapid curing while ensuring the long-term storage stability of the adhesive.
A photo-induced latent moisture curing catalyst was used, combined with a stepwise asymmetric end-capping process and a low-temperature light-shielding preparation process, to construct an active linkage mechanism between photocuring and moisture curing. The catalyst releases catalytic alkoxysilane groups through photolysis reaction to achieve deep curing and maintain the chemical inertness of the catalyst during storage.
It significantly improves the curing reaction rate in shaded areas, ensuring the stability of the adhesive during storage and the efficiency of deep curing, and providing reliable curing strength in non-standard humidity environments.
Smart Images
Figure CN121975482A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of UV moisture-curing adhesive technology, and in particular to an LED UV moisture-curing adhesive and its preparation method. Background Technology
[0002] With the rapid development of electronic packaging technology, in order to protect printed circuit boards (PCBs) and electronic components from the effects of environmental moisture, chemical corrosion and mechanical impact, ultraviolet (UV) curing adhesives have been widely used in the field of electronic assembly due to their advantages such as fast curing speed, high production efficiency and suitability for assembly line operations. With increasingly stringent environmental regulations and rising energy-saving requirements, traditional mercury lamp light sources are gradually being replaced by LED UV light sources that have lower energy consumption, longer lifespan and no ozone generation. This has made LED-based curing materials a hot topic in industry research and development.
[0003] However, in practical applications, the structure of electronic components is becoming increasingly complex and the integration level is constantly improving. Light often has difficulty penetrating the bottom of the component or the gaps between densely arranged pins, which makes it impossible for these shaded areas to be cured by ultraviolet light irradiation. To solve this problem, the industry usually adopts a dual curing strategy, which introduces a moisture curing mechanism (such as isocyanate or alkoxysilane) into the UV curing system. The aim is to achieve rapid shaping of the adhesive surface through light irradiation, and then use the moisture in the environment to achieve delayed curing of the shaded parts.
[0004] Although existing UV-moisture dual curing technology has alleviated the problem of shadow curing to some extent, it still faces significant technical bottlenecks in practical applications. In existing dual curing systems, the photocuring reaction and the moisture curing reaction are usually two independent parallel processes. The light is only responsible for initiating free radical polymerization and has no active promoting effect on the moisture curing process. This results in the curing of the shadow area being completely passive, and its reaction rate is extremely dependent on the ambient humidity and the diffusion rate of moisture. In dry environments or deep potting scenarios, the shadow area often takes several days or even weeks to fully cure, which seriously affects the product's turnover efficiency and final performance.
[0005] Secondly, to improve the rate of moisture curing, existing technologies often add highly active organotin or organobismuth catalysts to the formulation. However, this conventional catalytic method brings an irreconcilable contradiction: highly active catalysts can slowly initiate reactions during adhesive storage (even in a sealed container) due to trace amounts of moisture or thermal history, causing the adhesive viscosity to rise too quickly or even gel, greatly shortening the product's shelf life. Conversely, if the amount of catalyst is reduced to ensure storage stability, the shaded areas after application will not cure completely or become sticky. In addition, in terms of resin matrix selection, existing technologies mostly adopt a simple physical blending method, that is, directly mixing the photocurable resin and the moisture-curable resin. Due to the differences in polarity and molecular structure between the two types of resins, simple blending often leads to poor system compatibility, and micro-phase separation is prone to occur during the curing process, resulting in a hazy appearance and reduced light transmittance of the cured product. Furthermore, due to the lack of organic bonds, the cured adhesive layer is prone to microcracks under internal stress, making it difficult to meet the stringent requirements of high-end electronic packaging for material mechanical and optical properties. Summary of the Invention
[0006] The purpose of this invention is to provide an LED UV moisture-curing adhesive and its preparation method, which solves the problems of passive and slow curing reaction in the shadow area, heavy dependence on ambient humidity, and difficulty in achieving deep and rapid curing while ensuring the long-term storage stability of the adhesive in the existing LED UV moisture dual curing system.
[0007] To achieve the above objectives, the present invention provides the following technical solution: an LED UV moisture-curing adhesive, comprising the following components by mass percentage: Dual-cured polyurethane acrylate resin: 40%-60%; Reactive diluent: 10%-30%; LED photoinitiator: 1%-5%; Photoinduced latent moisture-curing catalyst: 2%-8%; Chemical dehydrating agent: 0.5%-2%; Functional additives: 1%-6%; The sum of the mass percentages of all components is 100%. The main chain of the dual-cured polyurethane acrylate resin is a polyurethane segment, and the molecular chain is simultaneously grafted with acryloyloxy and alkoxysilane groups. The photo-induced latent moisture-curing catalyst is a compound that undergoes a photolysis reaction under LED UV light and releases an active substance that catalyzes the hydrolysis and condensation of alkoxysilane groups.
[0008] A method for preparing an LED UV moisture-curing adhesive includes the following steps: S1. Synthesis of dual-cured polyurethane acrylate resin: Diisocyanate is reacted with polypolyol to generate a prepolymer, and then the prepolymer is reacted with hydroxyl-containing acrylate monomer and active hydrogen silane coupling agent respectively to obtain the dual-cured polyurethane acrylate resin. S2. Preparation of catalyst mother liquor: Under light-protected conditions, the photo-induced latent moisture-curing catalyst is dispersed and dissolved in a portion of the formulated amount of active diluent to obtain a homogeneous catalyst mother liquor. S3. Dehydration and compounding: The synthesized dual-cured polyurethane acrylate resin, the remaining amount of the formulated reactive diluent, chemical dehydrating agent and functional additives are mixed and dehydrated under vacuum conditions to obtain a dehydrated base material. S4. Final mixing and packaging: Under light-protected and temperature-controlled conditions, the LED photoinitiator and the prepared catalyst mother liquor are added to the dehydrated base material, mixed evenly, filtered and packaged to obtain the LED UV moisture-curing adhesive.
[0009] Preferably, in the step of synthesizing dual-curing polyurethane acrylate resin, a stepwise asymmetric end-capping process is adopted. The specific reaction control process is as follows: first, the diisocyanate and the polyol are subjected to a chain extension reaction at a temperature of 75-85°C until the isocyanate group content in the system drops to 50%±5% of the theoretical value; The system was then cooled to 45-55°C, and the hydroxyl-containing acrylate monomer was added dropwise. The reaction was maintained at this temperature until half of the isocyanate group content was consumed. Finally, the system temperature was controlled at 40-50℃, and the active hydrogen silane coupling agent was added dropwise. The reaction continued until infrared spectroscopy showed that the characteristic peaks of the isocyanate group had completely disappeared.
[0010] Preferably, in the stepwise asymmetric end-capping process, the feeding ratio of each reactant satisfies the following conditions: the molar ratio of the diisocyanate to the polypolyol is 2.0-2.2; the amount of the hydroxyl-containing acrylate monomer added is 45%-55% of the molar amount of the remaining isocyanate groups; and the amount of the active hydrogen silane coupling agent added is equimolar to the final remaining isocyanate groups.
[0011] Preferably, in the step of preparing the catalyst mother liquor, the process parameters are controlled as follows: The light-shielding condition is a yellow light source environment, and the temperature is controlled at 15-25℃ throughout the preparation process; the amount of the active diluent used to prepare the mother liquor is 20%-30% of the total amount of active diluent in the formula; the stirring speed during the dispersion and dissolution process is 400-800 rpm, and the stirring time is 20-40 minutes.
[0012] Preferably, in the dehydration and compounding steps, the process parameters and pretreatment controls are as follows: The vacuum level is controlled between -0.090 MPa and -0.098 MPa, and the holding time is 30-45 minutes. Before being added to the mixture, the functional additives need to be vacuum dried at 110-130°C for 4-6 hours.
[0013] Preferably, in the final mixing and packaging steps, the process parameters are controlled as follows: The temperature control condition is that the material temperature is forcibly controlled to not exceed 30°C by a cooling device. The mixing process is carried out under a vacuum of better than -0.095 MPa, with the dispersion speed controlled at 300-500 rpm and the mixing time at 15-20 minutes.
[0014] Preferably, the specific selection of the photo-induced latent moisture-curing catalyst and the LED photoinitiator is as follows: The photoinduced latent moisture curing catalyst is selected from one or more of the quaternary ammonium salt derivatives of tetraphenylborate or photocatalytic amine-producing carbamate compounds; The LED photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.
[0015] Preferably, the raw materials for synthesizing the dual-curing polyurethane acrylate resin are specifically selected as follows: The hydroxyl-containing acrylate monomer is selected from hydroxyethyl acrylate or hydroxypropyl acrylate; The active hydrogen-containing silane coupling agent is selected from 3-aminopropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane.
[0016] Preferably, the specific selection of the reactive diluent and the chemical dehydrating agent is as follows: The reactive diluent is selected from one or more of isobornyl acrylate, acrylomorpholine, and 1,6-hexanediol diacrylate; The chemical dehydrating agent is selected from vinyltrimethoxysilane or vinyltriethoxysilane.
[0017] In summary, the present invention has at least one of the following beneficial technical effects: 1. This invention introduces a photo-induced latent moisture curing catalyst to construct an active linkage mechanism between photocuring and moisture curing. This allows light to not only complete the instantaneous shaping of the surface layer, but also activate a highly active moisture curing catalyst for the deep or shaded areas. As a result, the subsequent moisture curing reaction no longer depends entirely on the natural penetration of ambient humidity, significantly improving the reaction rate of the shaded area to solidify inward.
[0018] 2. This invention synthesizes dual-curing polyurethane acrylate resin through a stepwise asymmetric end-capping process, which effectively solves the problems of micro-phase separation and light transmittance of the adhesive layer. This molecular structure design ensures that the two reaction networks grow on the same molecular backbone during the curing process, forming a uniform organic whole, and avoiding the phenomenon of fogging, whitening or uneven mechanical properties of the adhesive layer caused by poor component compatibility.
[0019] 3. This invention fundamentally solves the contradiction between high reactivity and long shelf life by using a photo-induced latent catalyst in conjunction with a strict dehydration and low-temperature light-protection preparation process. By utilizing the chemical inertness of the catalyst under light-protection conditions, combined with the dehydration of the base material and the low-temperature final mixing process, the adhesive is ensured to be in a dormant state during storage, and is immediately awakened upon exposure to light when used, thus achieving both excellent storage stability and excellent deep curing efficiency.
[0020] 4. By utilizing the high activity and diffusion characteristics of photolysis products, this invention significantly reduces the dependence of the moisture curing process on environmental humidity. Even in application environments with low relative humidity, sufficient catalytic active centers (such as tertiary amines) have been released during the photoinitiation stage. These active substances can rapidly initiate the hydrolysis and condensation reaction of alkoxysilanes using extremely small amounts of moisture inside the adhesive layer or even adsorbed water on the substrate surface, and penetrate into the un-illuminated areas with the concentration gradient, thereby ensuring reliable final curing strength even in non-standard humidity environments.
[0021] 5. This invention ensures the effectiveness of sensitive components and the consistency of product quality through a specific catalyst mother liquor pre-dispersion and low-temperature final mixing process. Addressing the characteristics of photocatalysts, which are mostly solids and sensitive to heat / light, this invention first pre-disperses them into a homogeneous mother liquor in a low-temperature, light-protected environment and on an active diluent carrier. Then, it introduces the mother liquor into the main system under anhydrous low-temperature conditions. This process avoids the premature catalyst failure caused by localized high temperatures that may result from prolonged high-shear stirring in large-scale production equipment, ensuring the stability of the photosensitivity and curing performance of each batch of adhesive. Attached Figure Description
[0022] Figure 1 This is one of the schematic diagrams of the preparation method of the present invention; Figure 2 This is a second schematic diagram of the preparation method of the present invention; Figure 3 This is the third schematic diagram of the preparation method of the present invention; Figure 4 This is the fourth schematic diagram of the preparation method of the present invention; Figure 5 This is the fifth schematic diagram of the preparation method of the present invention. Detailed Implementation
[0023] The following is in conjunction with the appendix Figure 1 - Appendix Figure 5 The present invention will be further described in detail below.
[0024] This invention provides an LED UV moisture-curing adhesive, comprising the following components by weight percentage: Dual-cured polyurethane acrylate resin: 40%-60%; Reactive diluent: 10%-30%; LED photoinitiator: 1%-5%; Photoinduced latent moisture-curing catalyst: 2%-8%; Chemical dehydrating agent: 0.5%-2%; Functional additives: 1%-6%; The sum of the mass percentages of all components is 100%. The main chain of the dual-curing polyurethane acrylate resin is a polyurethane segment, and the molecular chain is simultaneously grafted with acryloyloxy and alkoxysilane groups. Photoinduced latent moisture curing catalysts are compounds that undergo photolysis under LED UV light irradiation and release active substances that catalyze the hydrolysis and condensation of alkoxysilane groups; Specifically, the components (by mass percentage) and their specific implementation and function are as follows for the LED UV moisture-curing adhesive prepared according to the above method: Dual-curing polyurethane acrylate resin (40%-60%): As the main body of film formation, it provides the basic mechanical strength and toughness of the adhesive layer. Its asymmetrical structure at both ends ensures that the adhesive layer can be quickly shaped under light and can react with moisture to crosslink in the dark. Reactive diluent (10%-30%): Selected from isobornyl acrylate (IBOA), acrylamide (ACMO) or 1,6-hexanediol diacrylate (HDDA). Its function is to adjust the viscosity of the system to suit the sizing process, and at the same time participate in the free radical photocuring reaction to become part of the crosslinking network. LED photoinitiator (1%-5%): Selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO). These initiators have high light absorption efficiency at long wavelengths (365-405nm) of LEDs and are responsible for initiating the free radical polymerization of acrylate double bonds. Photoinduced latent moisture-curing catalyst (2%-8%): This is the core functional component of the present invention, selected from tetraphenylborate limonium salt derivatives or photocatalytic amine-producing carbamate compounds; Chemical dehydrating agent (0.5%-2%): Selected from vinyltrimethoxysilane (VTMO) or vinyltriethoxysilane, used to capture moisture that may seep in during production and storage, ensuring storage stability; Functional additives (1%-6%) include hydrophobic fumed silica (to adjust thixotropy), silicone defoamers, etc. The curing adhesive prepared based on the above components solves the problem of shadow curing through the following mechanism: Photocuring stage (surface setting): When the adhesive is irradiated by LED UV light, the LED photoinitiator absorbs light energy to generate free radicals, which initiate the polymerization reaction of acrylate double bonds in the resin and reactive diluent, achieving rapid curing and setting of the adhesive surface (in seconds). Activation of latent catalyst (linkage trigger): At the same time, the LED UV light will also be absorbed by the photoinduced latent moisture curing catalyst, which will undergo photolysis reaction and release highly active strong bases (such as tertiary amines) or Lewis acids in situ. Moisture curing stage (dark reaction): The released strong alkaline substances are highly efficient catalysts for the hydrolysis and condensation of alkoxysilanes. After the light exposure ends, these photo-unlocked catalysts penetrate into the interior of the adhesive layer. Even under low ambient humidity, they can significantly accelerate the reaction between alkoxysilane groups and trace amounts of moisture in the resin. Curing in shaded areas: For deep areas that are completely unexposed to light, although the catalyst is not photolyzed, the alkoxysilane groups in the resin have moisture curing capabilities, and the active amines generated by surface photolysis diffuse into the interior to a certain extent, thus ensuring the final curing of the whole and forming an interpenetrating network structure. Through the specific selection of components and control of the preparation process, the catalyst in the adhesive is kept in an inert state during the storage period (in a light-free and water-free environment), which has excellent storage stability. When used, the dual mechanism of triggering free radical polymerization and moisture curing catalyst release by light exposure is utilized to achieve efficient construction operations.
[0025] Based on the aforementioned overall scheme and the scope of the claims, the following specific embodiments are constructed, demonstrating the technical focus under different component and process parameter ratios. The embodiments are as follows: Basic Example 1: Using 50% prepolymer resin, 3% photoinitiator, 5% moisture curing catalyst, 20% reactive diluent, and 2% silica filler, the test results showed that under standard conditions, the curing time was 2 minutes and the bonding strength reached 10 MPa. Basic Example 2: 48% prepolymer resin, 2.5% photoinitiator, 4% moisture curing catalyst, 22% reactive diluent, 3.5% silica filler, curing time test result is 1.5 minutes, and the bonding strength reaches 12 MPa; Optimized Example 1: Based on the basic example, the prepolymer resin was adjusted to 52%, the photoinitiator to 3.5%, the moisture curing catalyst to 4.5%, the reactive diluent to 18%, the silica filler to 2%, and 0.5% silver powder was added as a conductive filler. The test results showed that the curing time was shortened to 1.2 minutes, the bonding strength was increased to 14 MPa, and the electromagnetic shielding effectiveness reached 20 dB. Optimized Example 2: 50% prepolymer resin, 3% photoinitiator, 5% moisture curing catalyst, 20% reactive diluent, 2% silica filler, and 1% copper powder added. The test results showed that the curing time was 1.4 minutes, the bonding strength reached 13 MPa, and the electromagnetic shielding effectiveness reached 18 dB. Extended Example 1: Based on the basic scheme, an additional 3% copper powder is added, the curing time is 1.6 minutes, the bonding strength reaches 11MPa, and the electromagnetic shielding effectiveness reaches 15dB; Extended Example 2: 49% prepolymer resin, 2.8% photoinitiator, 4.2% moisture curing catalyst, 21% reactive diluent, 3% silica filler, 2% silver powder added, curing time is 1.3 minutes, the bonding strength reaches 15MPa, and the electromagnetic shielding effectiveness reaches 22dB.
[0026] A method for preparing an LED UV moisture-curing adhesive includes the following steps: S1. Synthesis of Dual-Cure Polyurethane Acrylic Resin: Diisocyanate is reacted with a polyol to generate a prepolymer. The prepolymer is then reacted stepwise with a hydroxyl-containing acrylate monomer and a silane-containing coupling agent to obtain the dual-cured polyurethane acrylate resin. In the synthesis of the dual-cured polyurethane acrylate resin, a stepwise asymmetric end-capping process is employed. The specific reaction control process is as follows: First, the diisocyanate and polyol undergo a chain extension reaction at 75-85℃ until the isocyanate group content in the system drops to 50%±5% of the theoretical value; then, the system is cooled to 45-55℃, and dropwise... Add hydroxyl-containing acrylate monomers and maintain the reaction temperature until half of the isocyanate groups are consumed. Finally, control the system temperature at 40-50℃, add an active hydrogen silane coupling agent dropwise, and continue the reaction until infrared spectroscopy shows that the characteristic peaks of the isocyanate groups have completely disappeared. In the stepwise asymmetric end-capping process, the feeding ratio of each reactant meets the following conditions: the molar ratio of diisocyanate to polyol is 2.0-2.2; the amount of hydroxyl-containing acrylate monomers added is 45%-55% of the molar amount of the remaining isocyanate groups; the amount of active hydrogen silane coupling agent added is equimolar to the final remaining isocyanate groups. Specifically, this step aims to prepare a polyurethane polymer containing both a photosensitive group (acryloyloxy) and a moisture-curing group (alkoxysilyl) in its molecular structure. To ensure the orderly distribution of the two groups on the molecular chain and to prevent side reactions during synthesis, a stepwise asymmetric end-capping process is employed. Prepolymerization stage: Dry nitrogen gas is introduced into the reactor for protection. Diisocyanate (e.g., isophorone diisocyanate IPDI) and polyol (e.g., polytetrahydrofuran ether diol PTMEG) are mixed, controlling the molar ratio of diisocyanate to polyol to be 2.0-2.2. Dibutyltin dilaurate was subjected to a chain extension reaction at a temperature of 75-85℃. During the reaction, the content of isocyanate groups (-NCO) was measured at regular intervals until the content of -NCO dropped to 50%±5% of the theoretical value. At this point, the molecular chain mainly exhibited the characteristics of a polyurethane prepolymer with -NCO groups at both ends.
[0027] Photosensitive group introduction stage (semi-end-capping): The reaction system temperature is lowered to 45-55℃, a polymerization inhibitor (such as p-hydroxyanisole MEHQ) is added, followed by the dropwise addition of hydroxyl acrylate monomers (such as hydroxyethyl acrylate HEA), with the amount added controlled to be 45%-55% of the remaining NCO molar amount. The reaction is maintained at 50-60℃ until half of the -NCO content is detected to be consumed. This step utilizes a lower temperature and stoichiometry to preferentially convert some -NCO groups into photocurable double bond end groups.
[0028] Moisture-curing group introduction stage (final end-capping): The system temperature is further controlled at 40-50℃ (using low temperature to prevent silane coupling agent self-polymerization), and an active hydrogen-containing silane coupling agent (such as 3-aminopropyltrimethoxysilane APTMS or 3-mercaptopropyltrimethoxysilane) is added dropwise. The amount added is equimolar of the final remaining -NCO. The reaction continues until the infrared spectrum (FT-IR) shows 2270. The complete disappearance of the -NCO characteristic absorption peak at the point indicates that the resin synthesis is complete.
[0029] S2. Preparation of catalyst mother liquor: Under light-protected conditions, the photo-induced latent moisture-curing catalyst is dispersed and dissolved in a portion of the active diluent in the formulation to obtain a homogeneous catalyst mother liquor. In the step of preparing the catalyst mother liquor, the process parameters are controlled as follows: the light-protected conditions are a yellow light source environment, and the temperature is controlled at 15-25℃ throughout the preparation process; the amount of active diluent used to prepare the mother liquor is 20%-30% of the total amount of active diluent in the formulation; the stirring speed during the dispersion and dissolution process is 400-800 rpm, and the stirring time is 20-40 minutes. Specifically, under strict light-protection conditions (yellow light source environment), 20%-30% of the total amount of active diluent in the formula is selected as the carrier solvent, and a photoinduced latent moisture-curing catalyst (such as a quaternary ammonium salt derivative of tetraphenylborate or a photolysis-producing amine-type carbamate compound) is added to it. Under the condition of temperature control at 15-25℃, the mixture is stirred and dispersed at a speed of 400-800 rpm for 20-40 minutes until a homogeneous transparent or semi-transparent solution is formed. This mother liquor is used as the initiator seed and sealed for later use.
[0030] S3. Dehydration and Compounding: The synthesized dual-cured polyurethane acrylate resin, the remaining reactive diluent in the formulation, the chemical dehydrating agent, and the functional additives are mixed and dehydrated under vacuum conditions to obtain a dehydrated base material. In the dehydration and compounding steps, the process parameters and pretreatment controls are as follows: the vacuum degree is controlled between -0.090MPa and -0.098MPa, and the holding time is 30-45 minutes; the functional additives need to be vacuum dried at 110-130℃ for 4-6 hours before being added to the mixture. Specifically, this step can prevent moisture-cured groups from prematurely hydrolyzing during storage.
[0031] Filler pretreatment: Place the functional additives (mainly thixotropic agents such as fumed silica) in a vacuum oven and vacuum dry them at 110-130℃ for 4-6 hours to remove physically adsorbed water; Dehydration of base material: The dual-cured polyurethane acrylate resin obtained in step S1, the remaining reactive diluent in the formulation, the chemical dehydrating agent (such as vinyltrimethoxysilane), and the dried functional additives are put into a vacuum mixer. Process control: Start stirring and control the vacuum degree between -0.090 MPa and -0.098 MPa for 30-45 minutes. During this process, the chemical dehydrating agent will preferentially react with the trace amounts of residual moisture in the system to obtain a deeply dehydrated base material.
[0032] S4. Final Mixing and Packaging: Under light-protected and temperature-controlled conditions, add the LED photoinitiator and the prepared catalyst mother liquor to the dehydrated base material. After mixing evenly, filter and package to obtain the LED UV moisture-curing adhesive. In the final mixing and packaging steps, the process parameters are controlled as follows: Temperature control is achieved by forcibly controlling the material temperature to not exceed 30℃ using a cooling device; the mixing process is carried out under a vacuum degree better than -0.095 MPa, the dispersion speed is controlled at 300-500 rpm, and the mixing time is 15-20 minutes. The specific selection of the photo-induced latent moisture-curing catalyst and the LED photoinitiator is as follows: The photo-induced latent moisture-curing catalyst is selected from one or more of the quaternary ammonium salt derivatives of tetraphenylborate or photocatalytic amine-producing carbamate compounds; the LED photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The specific selection of raw materials for the synthesis of various dual-curing polyurethane acrylate resins is as follows: hydroxyl-containing acrylate monomers are selected from hydroxyethyl acrylate or hydroxypropyl acrylate; active hydrogen silane coupling agents are selected from 3-aminopropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane; and reactive diluents and chemical dehydrating agents are selected as follows: reactive diluents are selected from one or more of isobornyl acrylate, acrylomorpholine, and 1,6-hexanediol diacrylate; and chemical dehydrating agents are selected from vinyltrimethoxysilane or vinyltriethoxysilane.
[0033] Specifically, this step is the key step in introducing the latent catalytic system into the main system; Low temperature control: Cooling medium is introduced into the mixer jacket to force the temperature of the material inside the vessel to not exceed 30°C. This is to prevent the photo-induced latent catalyst from undergoing thermal decomposition in the shear heat generated during mixing. Addition and mixing: Under light-protected conditions, add LED photoinitiator (such as TPO, 819) and the catalyst mother liquor prepared in step S2 to the dehydrated base material; Gentle dispersion: Under vacuum conditions better than -0.095MPa, use a low-shear dispersion mode (dispersion speed 300-500rpm) to mix for 15-20 minutes to ensure uniform distribution of initiator and catalyst without destroying the latent state; Post-processing: The mixed adhesive solution is filtered under pressure through a 200-400 mesh filter and filled into black opaque UV barrier tubes, which are then sealed with nitrogen.
[0034] In summary, this invention provides an LED UV moisture-curing adhesive and its preparation method. By introducing a photo-induced latent moisture-curing catalyst, an active linkage mechanism between photocuring and moisture curing is constructed. In traditional dual-curing adhesives, photocuring and moisture curing are usually independent processes that do not interfere with each other. However, this invention utilizes LED ultraviolet light of a specific wavelength to trigger the decomposition of the photo-induced latent catalyst, releasing highly active amines or alkaline substances in situ. This allows the light irradiation to not only complete the instantaneous shaping of the surface layer but also activate the highly active moisture-curing catalyst in the deep or shaded areas. This makes the subsequent moisture curing reaction no longer completely dependent on the natural penetration of ambient humidity, significantly improving the reaction rate of inward curing in the shaded areas. Furthermore, by using a photo-induced latent catalyst in conjunction with a strict dehydration and low-temperature light-shielding preparation process, the contradiction between high reactivity and long shelf life is fundamentally solved. By utilizing the chemical inertness of the catalyst under light-shielding conditions, combined with the dehydration of the base material and the low-temperature final mixing process during preparation, the adhesive is ensured to remain dormant during storage and is immediately awakened upon light irradiation when used, thus simultaneously achieving excellent storage stability and excellent deep curing efficiency.
[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. An LED UV moisture-curing adhesive, characterized in that, The components include the following mass percentages: Dual-cured polyurethane acrylate resin: 40%-60%; Reactive diluent: 10%-30%; LED photoinitiator: 1%-5%; Photoinduced latent moisture-curing catalyst: 2%-8%; Chemical dehydrating agent: 0.5%-2%; Functional additives: 1%-6%; The sum of the mass percentages of all components is 100%. The main chain of the dual-cured polyurethane acrylate resin is a polyurethane segment, and the molecular chain is simultaneously grafted with acryloyloxy and alkoxysilane groups. The photo-induced latent moisture-curing catalyst is a compound that undergoes a photolysis reaction under LED UV light and releases an active substance that catalyzes the hydrolysis and condensation of alkoxysilane groups.
2. A method for preparing an LED UV moisture-curing adhesive, characterized in that, The LED UV moisture-curing adhesive according to claim 1 includes the following steps: S1. Synthesis of dual-cured polyurethane acrylate resin: Diisocyanate is reacted with polypolyol to generate a prepolymer, and then the prepolymer is reacted with hydroxyl-containing acrylate monomer and active hydrogen silane coupling agent respectively to obtain the dual-cured polyurethane acrylate resin. S2. Preparation of catalyst mother liquor: Under light-protected conditions, the photo-induced latent moisture-curing catalyst is dispersed and dissolved in a portion of the formulated amount of active diluent to obtain a homogeneous catalyst mother liquor. S3. Dehydration and compounding: The synthesized dual-cured polyurethane acrylate resin, the remaining amount of the formulated reactive diluent, chemical dehydrating agent and functional additives are mixed and dehydrated under vacuum conditions to obtain a dehydrated base material. S4. Final mixing and packaging: Under light-protected and temperature-controlled conditions, the LED photoinitiator and the prepared catalyst mother liquor are added to the dehydrated base material, mixed evenly, filtered and packaged to obtain the LED UV moisture-curing adhesive.
3. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, In the synthesis of dual-curing polyurethane acrylate resin, a stepwise asymmetric end-capping process is adopted. The specific reaction control process is as follows: First, the diisocyanate and the polyol are subjected to a chain extension reaction at a temperature of 75-85°C until the isocyanate group content in the system drops to 50%±5% of the theoretical value. The system was then cooled to 45-55°C, and the hydroxyl-containing acrylate monomer was added dropwise. The reaction was maintained at this temperature until half of the isocyanate group content was consumed. Finally, the system temperature was controlled at 40-50℃, and the active hydrogen silane coupling agent was added dropwise. The reaction continued until infrared spectroscopy showed that the characteristic peaks of the isocyanate group had completely disappeared.
4. The method for preparing an LED UV moisture-curing adhesive according to claim 3, characterized in that, In the stepwise asymmetric end-capping process, the feeding ratio of each reaction raw material satisfies the following conditions: the molar ratio of the diisocyanate to the polypolyol is 2.0-2.2; the amount of the hydroxyl-containing acrylate monomer added is 45%-55% of the molar amount of the remaining isocyanate groups; and the amount of the active hydrogen silane coupling agent added is equimolar to the final remaining isocyanate groups.
5. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, In the step of preparing the catalyst mother liquor, the process parameters are controlled as follows: The light-shielding conditions are a yellow light source environment, and the temperature is controlled at 15-25℃ throughout the preparation process; the amount of the active diluent used to prepare the mother liquor is 20%-30% of the total amount of active diluent in the formula; The stirring speed during the dispersion and dissolution process is 400-800 rpm, and the stirring time is 20-40 minutes.
6. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, The process parameters and pretreatment controls for the dehydration and compounding steps are as follows: The vacuum level is controlled between -0.090 MPa and -0.098 MPa, and the holding time is 30-45 minutes. Before being added to the mixture, the functional additives need to be vacuum dried at 110-130°C for 4-6 hours.
7. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, In the final mixing and packaging steps, the process parameters are controlled as follows: The temperature control condition is that the material temperature is forcibly controlled to not exceed 30°C by a cooling device. The mixing process is carried out under a vacuum of better than -0.095 MPa, with the dispersion speed controlled at 300-500 rpm and the mixing time at 15-20 minutes.
8. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, The specific selections of the photo-induced latent moisture-curing catalyst and the LED photoinitiator are as follows: The photoinduced latent moisture curing catalyst is selected from one or more of the quaternary ammonium salt derivatives of tetraphenylborate or photocatalytic amine-producing carbamate compounds; The LED photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.
9. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, The specific raw materials selected for the synthesis of the dual-curing polyurethane acrylate resin are as follows: The hydroxyl-containing acrylate monomer is selected from hydroxyethyl acrylate or hydroxypropyl acrylate; The active hydrogen-containing silane coupling agent is selected from 3-aminopropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane.
10. The method for preparing an LED UV moisture-curing adhesive according to claim 2, characterized in that, The specific selection of the reactive diluent and the chemical dehydrating agent is as follows: The reactive diluent is selected from one or more of isobornyl acrylate, acrylomorpholine, and 1,6-hexanediol diacrylate; The chemical dehydrating agent is selected from vinyltrimethoxysilane or vinyltriethoxysilane.